CN103376451A - Airborne double-waveband synthetic aperture radar system and method for measuring vegetation thickness utilizing same - Google Patents

Abstract

The invention discloses an airborne dual-band interference synthetic aperture radar system and a method for measuring vegetation thickness information by using the system. The airborne dual-band interference synthetic aperture radar system includes an airborne platform, an antenna system, a stable platform and distributed Type POS, the antenna system includes an L-band main transceiver antenna, two L-band secondary transceiver antennas and a Ka-band transceiver antenna group, the method includes: using the L-band main and secondary transceiver antenna baselines as a flexible Long baseline, use distributed POS to measure the positions of the phase centers of these three antennas, and obtain the time-varying information of the antenna phase centers during imaging. The signal received by the antenna is combined with the POS data for imaging processing; the imaging results of the L-band and Ka-band are subjected to interference processing to obtain the target scene DTM and the target scene DSM respectively; and the vegetation thickness information is obtained by subtracting the DTM and DSM . The invention expands the application scope of the airborne radar in the field of microwave remote sensing.

Description

Airborne Dual-band Synthetic Aperture Radar System and Its Method for Measuring Vegetation Thickness

technical field

The invention belongs to the field of Interferometric Synthetic Aperture Radar (Interferometric Synthetic ApertureRadar, InSAR) and microwave remote sensing technology, and specifically relates to an airborne dual-band synthetic aperture radar system and a method for measuring vegetation thickness using it, in particular to an airborne synthetic aperture radar system The method of obtaining the terrain information and surface vegetation information of the target scene by interferometric technology in the L and Ka dual bands.

Background technique

Airborne Interferometric Synthetic Aperture Radar (InSAR) has been relatively mature in the development of 3D imaging technology for target scenes, and the main working modes include single-antenna double-pass and dual-antenna single-pass. Compared with the double-pass method, the single-pass method can effectively overcome the problems of time decoherence and non-parallel flight paths, so it is widely used. In the single flight mode, it is divided into two working modes: one launch and double reception and spontaneous self-reception (ping-pong mode). The basic principle of interferometric altimetry is to use the interferometric phase to obtain the distance difference between the target and the phase center of the two antennas, use the distance relationship to obtain the target deflection angle, and then obtain the target height information (see Rosen P.A., Hensley S., Joughin I.R., et al.Synthetic ApertureRadar Interferometry[J].Proc.Of the IEEE, 2000, 88(3); Li Dao-jing, QiaoMing, Yin Jian-feng, Zhu Jin-biao, Xi Ying, Airborne MMW cross-trackInSAR system analysis, APSAR 2007[ C], Huangshan, China).

Millimeter-wave InSAR has attracted much attention due to its short wavelength, easy realization of high-resolution imaging, and high elevation accuracy under short baselines. A series of experimental systems have also been designed at home and abroad (see Dao-jing Li, Bo Liu, Zhou-hao Pan, et al.Airborne MMW InSAR Interferometry with cross-track three-baseline antennas[C].EUSAR 2012; Magnard C., Meier E., Rüegg M., et al.High Resolution Millimeter Wave SAR Interferometry[C] ]. IGARSS 2007. July 2007, Barcelona).

The extraction of vegetation (such as forest) thickness and main structure information is of great significance to the development of forestry and agricultural technologies such as biomass estimation and crop yield prediction. This technology has received extensive attention in the field of microwave remote sensing. At present, polarization interferometry has developed into a relatively effective method for vegetation thickness estimation, which uses appropriate modeling models such as RVoG, ERVoG, OVoG, etc. ]. Hefei: University of Science and Technology of China. 2011) Using the influence of P or L long-band signal attenuation on the polarization interference coefficient when penetrating vegetation to estimate terrain height and vegetation thickness and other information (see Papathanassiou K.P., Cloude S.R.Single- Baseline Polarimetric SAR Interferometry[J]. IEEE transactions on Geoscience and Remote Sensing. 2001, 39(11): 2352-2363; Garestier F., Dubois-Fernandez P.C., Champion I. Forest Height Inversion Using High-Resolution P-Band Plo-InSAR Data[J].IEEE transaction on Geoscience and Remote sensing, 2008, 46(11):3544-3559; Cloude S.R., P.P.K.Three-stage Inversion Process for Polarimetric SAR Interferometry[C].IEE Proceeding of Radar, Sonar and Navigation1, 25-03. 134).

The actual data processing results of relevant foreign experimental systems have shown the effectiveness of this method (see Bryan Mercer, Qiaoping Zhang, Marcus Schwaebisch, et al. Forest Height and Ground Topography at L-Band from an Experimental Single-PassAirborne PolInSAR System[C ]. PolInSAR 2009. January 2009, Italy).

When the long-wavelength-band-based polarization interferometry technique described above is used to estimate vegetation thickness, the estimation accuracy of terrain elevation is high, but the estimation accuracy of vegetation thickness is low. In actual use, the selection of processing models and model parameters has a strong relationship with the types and characteristics of ground vegetation. The specific performance is as follows: the RVoG model is more suitable when the anisotropy of the vegetation layer with polarization is not considered; if most of the branches of the tree species are located in the upper layer of the canopy, ERVoG is more suitable than RVoG; Structures such as tree trunks interact to make volume scattering show a certain directionality, so the OVoG model needs to be considered. The parameters involved in the above models are also related to the characteristics of ground vegetation. For example, the extinction coefficient is a physical quantity that characterizes the degree of attenuation of electromagnetic waves by the medium. Different vegetation has different extinction coefficients for electromagnetic waves of different bands. If the extinction coefficient is too small, it will be high. If the vegetation thickness is estimated, it will be underestimated otherwise.

Contents of the invention

(1) Technical problems to be solved

Technical problem to be solved by the present invention: the existing vegetation thickness measurement method based on polarization interference technology mainly has two shortcomings: one, the measurement accuracy of vegetation thickness depends on the selection of processing model and model parameters to a large extent, the selection The process relies on the prior information about the vegetation. Therefore, when the vegetation information in the target area is completely unknown, the measurement accuracy of the vegetation thickness will be greatly reduced; Second, even if the appropriate model and parameters are selected, the measurement accuracy of the vegetation thickness is still not good. high.

(2) Technical solution

In order to solve the above technical problems, the present invention proposes a vegetation thickness measurement method based on airborne dual-band synthetic aperture radar that does not require prior vegetation information in the target area and has high measurement accuracy.

An airborne dual-band interferometric synthetic aperture radar system according to the present invention includes an airborne platform, an antenna system, a stable platform, and a distributed POS. The antenna system includes an L-band main transceiver antenna and two L-band secondary transceivers. An antenna and a Ka-band transceiver antenna group; the L-band main transceiver antenna and two L-band secondary transceiver antennas are distributed and mounted on the carrier platform, and form a flexible long baseline interference relationship for obtaining terrain elevation information; The Ka-band transmitting and receiving antenna group is mounted on the stable platform to obtain vegetation canopy elevation information.

According to a preferred embodiment of the present invention, the distributed POS is composed of three independent POS, which are installed together with the L-band main transceiver antenna and the two L-band secondary transceiver antennas for measuring three The position and attitude information of an antenna during operation.

According to a preferred embodiment of the present invention, the carrier platform is an aircraft, and a pod is mounted under the wing of the aircraft, and the pod is used to install the L-band secondary transceiver antenna; and, on the aircraft's The belly position is equipped with the stable platform and the L-band main transceiver antenna, and the Ka-band transceiver antenna group is placed on the stable platform.

According to a preferred embodiment of the present invention, an optical window is opened downward on the belly of the aircraft, so that the L-band main transceiver antenna and the Ka-band transceiver antenna group can send and receive signals to the ground.

According to a preferred embodiment of the present invention, the Ka-band transmitting and receiving antenna group is mounted on a stable platform by adopting a rigid multi-baseline structure.

According to a preferred embodiment of the present invention, the L-band main and secondary transceiver antennas are fully polarized antennas, and phase sweeping is used in the azimuth direction, and the azimuth direction of the phase control beam is used to eliminate the influence of the aircraft drift angle.

According to a preferred embodiment of the present invention, the transmitter of the Ka-band transceiver antenna group uses a traveling wave tube amplifier.

According to a preferred embodiment of the present invention, the Ka-band transmitting and receiving antenna group is composed of a range wide beam antenna.

According to a preferred embodiment of the present invention, the stable platform includes a rotating mechanism for realizing left-view and right-view control of the Ka-band antenna group, and both the Ka-band antenna group and the rotating mechanism adopt self-rectification.

The present invention also proposes a method for measuring vegetation thickness information using an airborne dual-band interferometric synthetic aperture radar system. The airborne dual-band interferometric synthetic aperture radar system includes an airborne platform, an antenna system, a stable platform, and a distributed POS. The antenna system includes an L-band main transceiver antenna, two L-band secondary transceiver antennas and a Ka-band transceiver antenna group, and the L-band main transceiver antenna and two L-band secondary transceiver antennas are distributed on the carrier machine platform, and form a flexible long baseline interference relationship, the Ka-band transceiver antenna group is carried on the stable platform, it is characterized in that, the method includes the following steps: first, the L-band main and secondary transceiver The antenna baseline is used as a flexible long baseline, and the distributed POS is used to measure the positions of the phase centers of the three antennas to obtain the time-varying information of the antenna phase centers during imaging. At the same time, the Ka-band transceiver antenna group uses the stable platform for beam Stabilization and pointing control; then, the radar system is used for flight operations, and the signals received by each antenna are combined with POS data for imaging processing; then, polarization interference processing is performed on the imaging results of the L-band to obtain the target scene DTM, and perform interference processing on the Ka-band imaging results to obtain the target scene DSM; finally, subtract the target scene DTM from the target scene DSM to obtain the vegetation thickness information of the target scene.

(3) Beneficial effects

The airborne dual-band interferometric synthetic aperture radar system proposed by the invention uses the dual-band interferometric technology to measure the thickness of vegetation, expanding the application range of the airborne radar in the field of microwave remote sensing. The invention can realize the extraction of vegetation main structure information, the estimation of biomass, the prediction of crop yield, etc., and has great significance for the development of forestry and agriculture.

Description of drawings

Fig. 1 is a schematic diagram of the installation position of the antenna of the present invention;

Fig. 2 is a signal processing flowchart of the present invention;

Fig. 3 is a schematic diagram of L-band antenna right-looking interferometry of the present invention;

Fig. 4 is a schematic view of the aircraft outline structure and antenna installation position with Yun 12 as the carrier platform according to an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The airborne dual-band interferometric synthetic aperture radar system of the present invention includes an airborne platform, an antenna system, a stable platform, a distributed POS (Position and Orientation System) and an in-cabin unit.

The airborne platform is used to carry the stable platform, antenna system and cabin unit.

The stabilization platform is mounted on the carrier platform and is used for beam stabilization and pointing control of the Ka-band transceiver antenna group. According to a preferred embodiment of the present invention, it is the LH systemPAV series stabilized platform, which is a high-performance, high-reliability aerial gyro stabilized platform developed by Leica Corporation.

According to the present invention, the antenna system is distributed on the carrier platform and can send and receive signals to the ground. Therefore, the airborne platform should have enough space to carry the antenna system, and enable the antenna system to send and receive signals to the ground.

According to the present invention, the antenna system includes an L-band main transceiver antenna, two L-band secondary transceiver antennas and a Ka-band transceiver antenna group. The L-band main transceiver antenna and two L-band sub-transmitter antennas are mounted on the carrier platform in a distributed manner, and form a flexible long-baseline interference relationship for obtaining high-precision terrain elevation information; the Ka-band transceiver antenna The set is mounted on the stable platform to obtain high-precision vegetation canopy elevation information.

The distributed POS of the present invention is composed of three independent POS, which are installed together with one L-band main transceiver antenna and two L-band secondary transmitter-receiver antennas to measure the position and attitude information of the three antennas during operation .

The in-cabin unit is other conventional equipment required to ensure the operation of the system, including, for example, a display, an industrial computer, a power supply module, a GPS receiver and batteries, and data recording equipment.

A specific embodiment of the present invention will be described below with reference to FIG. 1 .

In this embodiment of the present invention, the carrier platform is an aircraft as shown in FIG. 1 , such as a transport aircraft. However, according to the present invention, the carrier platform can be any aircraft that can fly stably at a distance of 2-3.5 km from the ground.

As mentioned above, the airborne platform of the present invention is used to carry the stable platform, antenna system and cabin unit, so it should have a location and area for arranging the antenna system, cabin unit and stable platform.

In this embodiment, the aircraft shown in Figure 1 can mount pods under its wings to install the L-band secondary transceiver antenna; carry the stable platform and the L-band main transceiver antenna at the belly position of the aircraft , the Ka-band transceiver antenna group is placed on the stable platform, and an optical window is opened downward on the belly of the aircraft, so that the L-band main transceiver antenna and the Ka-band transceiver antenna group send and receive signals to the ground.

According to a kind of preferred embodiment of the present invention, as shown in Figure 4, can carry the pod that installs L-band sub-transmitting and receiving antenna at the auxiliary fuel tank position of the wing of aircraft, on the floor device in the cabin, slide rail is arranged, to facilitate installation cabin unit.

According to a preferred embodiment of the present invention, the L-band main transceiver antenna is mounted under the belly of the aircraft through a flipping mechanism, and the flipping mechanism is a device that is mounted under the belly of the aircraft and can be flipped left and right within a certain angle. The mechanical structure of the flip mechanism can make the L-band main transceiver antenna switch between left-view and right-view modes through the left-right flip operation of the flip mechanism, and can be formed with two L-band sub-transmitter antennas with independent left-view and right-view functions respectively. Flexible long-baseline interference relations.

According to a preferred embodiment of the present invention, the L-band main and secondary transceiver antennas both use fully polarized antennas, and adopt phase sweep in the azimuth direction, and use the phase to control the azimuth direction of the beam to solve the problem of aircraft drift angle bring about problems.

According to a preferred embodiment of the present invention, the Ka-band transceiver antenna group is mounted on a stable platform by adopting a rigid multi-baseline structure, and completes signal transmission and reception under the belly of the aircraft. The Ka-band transceiver antenna group includes a transmitter, the transmitter adopts a traveling wave tube (TWT) amplifier to realize high-power transmission, and adopts a distance-to-wide beam antenna to ensure the width, and the Ka-band transceiver antenna group is installed on a stable platform as a whole to realize beam Stabilization and pointing control, through the rotation of the stable platform to achieve left or right view. The stable platform includes a rotating mechanism for realizing left-view and right-view control of the Ka-band antenna group. The Ka-band antenna group and the rotating mechanism adopt self-rectification instead of the traditional radome rectification method.

The method for measuring vegetation thickness information by using the airborne dual-band interferometric synthetic aperture radar system of the present invention will be described below with reference to FIG. 2 .

First, the baselines of the L-band primary and secondary transceiver antennas are regarded as flexible long baselines, and the distributed POS of three nodes is used to measure the positions of the phase centers of the three antennas to obtain the time-varying information of the antenna phase centers during imaging. In later data processing, the concept of flexible baseline can be used for interference processing. The Ka-band transceiver antenna is rigidly connected with a multi-baseline structure and installed on a stable platform to achieve beam stabilization and pointing control.

Next, the radar system performs flight operations and ground data processing. During ground data processing, the signal received by each antenna is combined with the POS data for imaging processing. The imaging processing is a known technology.

Then, using the penetration ability of the L-band radar signal to the vegetation, the polarization interference processing is performed on the L-band imaging result to obtain the target scene DTM (Digital Terrain Model, digital terrain model); Echo-sensitive characteristics, the Ka-band imaging results are subjected to interference processing to obtain the target scene DSM (Digital Surface Model, digital surface model). In the process of obtaining DTM and DSM, the same calibration points in the two images need to be used, such as roads, buildings and other targets that can appear in both band images. The specific implementation method is introduced as follows in conjunction with Figure 3:

The interferometric phase can be expressed as

$\mathrm{<span\; class="notranslate">\; \&phi;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}\frac{\mathrm{<span\; class="notranslate">\; k\&Delta;R</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k\&pi;</span>}\mathrm{<span\; class="notranslate">\; B</span>}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; )</span>$

In the formula, λ is the carrier wavelength, and k=1 represents the interference of two antennas in the Ka-band one transmission and multiple receptions; k=2 represents the interference of the two antennas in the L-band ping-pong mode.

The elevation inversion formula is:

$\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; arcsin</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k\&pi;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$

In the formula, H represents the height of the carrier. The measurement errors σ H , σ B , σ R , σ φ and σ α of the parameters _H , _B , _R , _φ and _α will all cause elevation measurement errors. The elevation error components caused by these five parameters can be obtained by differentiation:

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}$

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; the\; tan</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{\mathrm{<span\; class="notranslate">\; B</span>}}$

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}$

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}$

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k\&pi;</span>}\mathrm{<span\; class="notranslate">\; B</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}$

Therefore, the size of the height measurement error caused by each parameter error can be estimated.

It should be pointed out that when processing L-band signals, the time-varying information of the baseline length and angle can be obtained according to the time-varying information of the antenna phase center recorded by the POS. It is not necessary to use the traditional method to compensate the antenna trajectory into two Parallel to the straight line, the interferogram can be obtained. A time-varying baseline will have time-varying height accuracy, height sensitivity, and unambiguous heights.

Finally, according to the DTM and DSM obtained in the above steps, the vegetation thickness information of the target scene can be obtained by subtracting the two.

For the airborne dual-band synthetic aperture radar vegetation thickness measurement method of the present invention, take Yun 12 as an example below as an aircraft platform, analyze performance information such as system parameters and elevation accuracy, unambiguous elevation of radar when the present invention is based on Yun 12 platform . As a specific embodiment of the present invention, Fig. 4 has provided the schematic diagram of the outline structure and antenna installation position of the aircraft with Yun 12 as the carrier platform.

The wingspan of the Y-12 aircraft is 19.2m, the height of the cabin is 1.96m, the auxiliary fuel tank is located in the middle of the wing, each loads 200kg, the cruising altitude of the aircraft is 3km, and the belly has an optical window adapted to the PAV platform. Table 1 to Table 3 show the parameters and elevation accuracy analysis results of the synthetic aperture radar system for dual-band vegetation thickness measurement carried by Yun-12 aircraft.

Table 1. Dual-band InSAR system parameters

Table 2. L-band InSAR parameter errors and corresponding elevation error components

Table 3. Ka-band InSAR parameter errors and corresponding elevation error components

According to the results in Table 2 and Table 3, it can be seen that the elevation of DTM acquired by L-band polarization interferometry can be designed to be 1.4m; the elevation accuracy of DSM acquired by Ka-band interferometry can be designed to be 0.5m. Based on the analysis of the above elevation accuracy, when the present invention uses the Y-12 aircraft as the carrier platform, the estimation accuracy of the vegetation thickness can be better than 2m.

When the distance from point P to the antenna is constant and the height increases by h, according to the geometric relationship, the change of the interference phase is:

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k\&pi;B</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}\frac{\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}$

The elevation sensitivity is: The unambiguous elevation is:

Under the system parameters in Table 1, the elevation sensitivity of the L-band working in the ping-pong mode imaging interferometric acquisition is 0.046rad/m, and the unambiguous elevation is 135.9m; m, and the unambiguous elevation is 32.0m. Ka-band unambiguous elevation can be extended to the required range through multiple baselines.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. an airborne two waveband interference synthetic aperture radar system comprises carrier aircraft platform, antenna system, stable platform and distributed POS, it is characterized in that,

Described antenna system comprises a L-band master dual-mode antenna, two secondary dual-mode antennas of L-band and a Ka wave band dual-mode antenna group;

Described L-band master dual-mode antenna and two secondary dual-mode antenna distribution formulas of L-band are equipped on the described carrier aircraft platform, and form flexible long base line interference relation, are used for obtaining landform altitude information;

Described Ka wave band dual-mode antenna group is equipped on the described stable platform, is used for obtaining vegetation canopy elevation information.

2. airborne two waveband interference synthetic aperture radar as claimed in claim 1 system, it is characterized in that, described distributed POS by three independently POS form, it is installed together with described L-band master dual-mode antenna and the secondary receipts antenna of sending out of described two L-bands respectively, is used for measuring position and the attitude information of three antennas between operational period.

3. airborne two waveband interference synthetic aperture radar as claimed in claim 1 system is characterized in that described carrier aircraft platform is an aircraft, and carry gondola below the wing of this aircraft, this gondola are used for installing the secondary dual-mode antenna of described L-band;

And, carry described stable platform and L-band master dual-mode antenna in the ventral position of described aircraft, lay Ka wave band dual-mode antenna group at stable platform.

4. airborne two waveband interference synthetic aperture radar as claimed in claim 3 system is characterized in that, has an optical window downwards at the ventral of described aircraft, so that described L-band master dual-mode antenna and Ka wave band dual-mode antenna group are to the ground receiving and transmitting signal.

5. airborne two waveband interference synthetic aperture radar as claimed in claim 3 system is characterized in that described Ka wave band dual-mode antenna group adopts many baselines of rigidity structure to articulate and is installed on the stable platform.

6. airborne two waveband interference synthetic aperture radar as claimed in claim 1 system, it is characterized in that the major and minor dual-mode antenna of described L-band all adopts the complete polarization antenna, and sweep mutually to adopting in the orientation, utilize the orientation of phase control wave beam to sensing, to eliminate the impact of aircraft drift angle.

7. airborne two waveband interference synthetic aperture radar as claimed in claim 1 system is characterized in that what the transmitter of described Ka wave band dual-mode antenna group adopted is travelling-wave tube amplifier (TWTA).

8. airborne two waveband interference synthetic aperture radar as claimed in claim 7 system is characterized in that described Ka wave band dual-mode antenna group is made of to broad beam antenna distance.

9. airborne two waveband interference synthetic aperture radar as claimed in claim 8 system, it is characterized in that, described stable platform comprises a rotating mechanism, looks with the right side for a left side of realizing Ka wave band antenna group and looks control, and described Ka wave band antenna group and this rotating mechanism all adopt voluntarily rectification.

10. method of utilizing in the claim 1 to 9 each described airborne two waveband interference synthetic aperture radar system to measure the vegetation thickness information, described airborne two waveband interference synthetic aperture radar system comprises the carrier aircraft platform, antenna system, stable platform and distributed POS, described antenna system comprises a L-band master dual-mode antenna, two secondary dual-mode antennas of L-band and a Ka wave band dual-mode antenna group, described L-band master dual-mode antenna and two secondary dual-mode antenna distribution formulas of L-band are equipped on the described carrier aircraft platform, and form flexible long base line interference relation, described Ka wave band dual-mode antenna group is equipped on the described stable platform, it is characterized in that described method comprises the steps:

At first, with the major and minor dual-mode antenna baseline of described L-band as the long baseline of flexibility, utilize distributed POS to measure the position of these three antenna phase centers, obtain the varying information of antenna phase center during imaging, simultaneously, described Ka wave band dual-mode antenna group is utilized described stable platform carry out the stable and sensing control of wave beam;

Then, with the operation of flying of described radar system, and the signal combination POS data that each antenna reception is arrived imaging processing respectively;

Then, the imaging results of described L-band is carried out polarization interference process, obtain target scene DTM, and described Ka wave band imaging results is interfered processing, obtain target scene DSM;

At last, described target scene DTM and target scene DSM are subtracted each other the vegetation thickness information that obtains the target scene.

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